Repeater for multiplex systems



H. A. AFFEL REPEATER FQR MULTIPLEX SYSTEMS May 12, 1925.

Filed Sept. 30, 1919 EJJ Z Um ATTORNEY Patented May 12, 1925.

HERMAN A. AFFEL, or

BROOKLYN, NEW YORK, ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPHCOMPANY, A CORPORATION OF NEW YORK.

REPEATER FOR MULTIPLEX SYSTEMS.

Application filed September 30, 1919. Serial No. 327,457.

State of New York,

concern I, HERMAN A.

Arrnn, n the county of have inventin Repeaters for which the followingto multiplex sigparticularly to resuch systems.

the invention rcsides in the provision of a repeater arrange;

ment for a multiplex carrier which separate amplifiers carrierfrequency.

amplifying each system in are provided for Another feature of theinvention resides in the provision of for a multiplex carrier plurality'sions may simultaneously pcat'ei' arrangement being a. repeaterarrangement system in which a of oppositely directed transmistake place,the reso organized that separate amplifiers will he provided for eachcarrier frcqucncy in each direction.

Another feature of the invention resides iii the provision of a repeaterarrangement of the character described in the paragraph, in which proseparate oppositely into the proper group of preceding vision is made todirected transmissions amplifiers and to furthcr separate the diflcrentfrequencies of the group of one-way transmissions, in order that theymay be applied to the proper amplifiers for amplificati Still anotherfeature of the invention resides in so arranging the transmittingchannels associated with one outgoing line and the receiving channelsassociated with another incoming line at an intermediate station thatthe transniitti channels may be intci-con amplifiers.associated with ngand receiving nected so that the the channels may constitute one-wayrepeaters for amplifying through carrier transmissions.

These features are realized in the organization set forth in thefollowing description and illustrated in the accompanying drawing, thefigure of which constitutes a circuit diagram of one embodiment of theinvention.

In the drawing, ML a two carrier transmission nd ML designate linesentering an intermediate station, which may be either a terminal stationforsignaling in opposite directions, or a through repeater station foramplifying signals transmitted from one line to the other. A commontransmitting circuit TL and a common receiving circuit RL are associatedwith the main line ML through a balanced transformer 10 and thesecircuits are rendered substantially conjugate by the provision of abalancing network MN, for balancing the main line ML. Similarly a commontransmitting circuit TL and a common receiving circuit R-L areassociated with the main line ML through a balanced transformer 10', anartificial line MN being provided for balancing the main line ML.

' A plurality of transmitting channels may be associated .with thecommon transmitting circuit TL through filters such as Tl? and TF Thesefilters may be of any desired character, such as tuned circuits resonantto the carrier frequency which it is desired to transmit. Similarly aplurality of receiving channels may be associated with the commonreceiving circuit R-L throu h filters or tuned circuits such as RF and Fthe tuned circuits being resonant to the carrier frequency which it isdesired to receive in a particularchannel. In a. like manner thetransmitting circuit TL is associated with transmitting channels throughtuned circuits TF and TF while the receiving circuit BL is associatedwith receivin channels throughtuned circuits such as RT, and RF In ordertosupplement the separation between oppositely directed channels, whichresults from rendering-the oominon trans=- n'iitting and receivingcircuits conjugate by means of the balancing artificial line, it may bedesirable that the frequencies used for transmission in oppositedirections should be different. The filters TF, and TF are thereforeindicated. as being resonant at frequencies f, and f res ectively whilethe corresponding filters F and RF, in the receiving channels areindicated as being resonant at frequencies f, and f The filters TF, andTF associated with the transmitting channels of the main line ML, mayhave assigned to them the same frequencies as filters RF and RF so alsofrequencies f, and 7, corresponding to the frequencies to which thefilters TF and TF are resonant may be assigned to the filters RF and RFassociated with the receiving channels of the line ML.

The transmitting channel related to the filter TF includes a vacuum tubeoscillator G1 of well-known type, the circuit of which is controlled bya transmitting relay TR, so

that telegraph signals may be translated into successions of trains ofoscillations generated by the oscillator G The frequency of thisoscillator, of course, the frequency of the filter TF An'amplifier TA isalso included in the channel, for amplifying the carrier frequencies tobe transmitted. This amplifier may be of any wellknown type, but isillustrated as a vac uum tube amplifier.

The receiving channel associated with the filter RF includes vacuum tubeamplifiers RA and R A for amplifyingreceived carrier frequencies and adetector 'D for translating the received frequencies into telegraphsignals. The detector may be of any well-known type, but is illustratedas a vacuum tube detector having in its output circuit receiving relayRR for repeating the received telegr. phic signals into a localreceiving circuit. I

Similarly the channel associated with the filter TF includes anoscillator G con trolled by a transmitting relay TR and an amplifier TAWhile the receiving channel associated with the filter RF, includesvacuum tube amplifiers RA R A as well as a detector D, having in itsoutput circuit a relay RR. The circuits of the various vacuum tubearrangements shown are all well known in the art and need not be furtherdescribed. It will be understood that similar--apparatus will beassociated with each of the other channels.

By means of the apparatus above described multiplex transmission maytake place in either direction between the station illustrated and adistant station, over the line ML, and likewise two-way multiplextransmission may take place over the line tween the station illustratedand another distant st atioli. In order that the apparatus illustratedmay be used for through repeating in connection with multiplextransmission taking place between the two distant stations over thelines ML and ML in tandem, means are provided for interconnectingoorresponding transmittin and receiving channels of the two lines, has aconnection 21 may be provided between the output circuit of theamplifier R A of the receivin channel associated with the filter RF anthe input circuit of the amplifier TA, of the transmitting channelassociated will correspond to" with the filter TF This connection may beclosed by means of a switch 8,. It will be noted that this connectiondoes not disable the detector D,, but merely diverts some of the outputenergy from the amplifier R A to the amplifier TA The detector,therefore, still functions to record at the intermediate station the lowfrequency signals, while the high frequency carrier currents may beamplified by the amplifiers RA R A TA, and transmit-ted from the line MLto the line ML. When thus operated on a repeater basis, the generator(Sr should be inoperative. Since the generator does not oscillate exceptwhen the transmitting relay TR is actuated, by merelyleaving the circuitof the transmitting relay TR open the generator-will be, in effect,disabled.

A similar connection 21 tween the amplifier B A, fier TA,, for repeatingin rection, said connection including a switch S,. It will beunderstood, of course, that similar connections may be made betweenother transmitting and receiving channels which have assigned to themthe same frequency.

Where the system is to be operated on a germinal basis, the switchessuch as S and will be open. By operating the transmitting relay TR,successive groups of carrier oscillations will be generated by thegenerator G amplified by the amplifier TA, and transmitted through thefilter TF to the common transmitting circuit TL. Similarly carrierfrequencies from the other transmitting channels may be simultaisprovided he and the amplineously imposed upon the circuit TL and theseveral carrier frequencies transmitted over the line ML to the distantstation. In coming carrier frequencies transmitted from the distantstation will pass through the transformer 10' to the common receivingcircuit RL and the frequcncieswill then be separated into the properreceiving channels by the filters such as RF, and RF The frequencypassed through the filter RF" is amplified by the amplifiers RA, and RA,and is then detected or translated into low frequency signaling impulsesby means of the detector D,, so that the receiving relay RR in theoutput circuit of the detector responds to the resultant direct currentimpulse and repeats said impulse to the local receiving circuit.Similarlyoutgoing transmissions may take place from the commontransmitting circuit TL and over. the main line ML to a distant terminalstation, while incoming transmissions from such station will be receivedby the common receiving circuit RL. As these operations will be similarto those already described, no further description is necessary.

When it is desired to operate the appathe opposite dimaintained open, so

ratus at the station illustrated, upon a through repeater basis, theswitches such as S and S, will be closed. Referring to the circuit 21,it will be seen that a high frequency connection extends from the plateof the amplifier 11 A over the conductor-21 to the input or grid of theamplifier TA,. The return circuit is through the ground, as thefilaments of both tubes are connected to ground. This connection acts asa shunt about the detector D,.. The circuit of the transmitting relay'TR, should now be that the generator G, is inactive.

Vith the circuit in this condition, high frequency carrier currentsincoming from the line ML are transmitted through the transformer 10 tothe common receiving circuit RL and the various frequencies are selectedby, means of the filters RF RF etc. into the proper channels. Thefrequency passed through he filter RF, is amplified by the amplifiers RAand B A, and part of the high frequency energy is then transmitted overthe path 21 to the amplifier TA said energy being further amplified bysaid amplifier TA, and transmitted through the filter TF and over thecircuit TL to the main line ML. Some of the high frequency energy fromthe output circuit of the tube T,A is also impressed upon the detector Dand is thereby translated into low frequency signals toactuatethe-receiving relay RR, so that the signals which are imposedupon the repeated carrier transmission may be recorded at the repeaterstation. This provides a simple method of monitoring the action of therepeaters.

The action of the channels interconnected through the switch 5,, as wellas the remaining channels which are not illustrated, will be similar tothat already described and need not be further referred to.

It will be obvious thatthe general principles-herein disclosed may beembodied in many other organizations widely different from thoseillustrated, without departing from the spirit of the invention asdefined in the following claims:

What is claimed is: h r

1. Ina signaling system, .a transmission line. means for simultaneouslytransmitting in one direction over said line a plurality of signals bymeans of carrier currents of a plurality of different frequencies, meansfor simultaneously transmitting in the opposite direction over saidlinea plurality of signals by means of carrier currents of a pluralityof different frequencies, a one-way repeater in said line at anintermediate point for each carrier frequency transmitted in onedirection, selective means on'the input side of each repeater forselecting thereto the carrier frequency to be amplified thereby, andselective means on, the output side of said on the input side of eachrepeater repeater for preventing carrier frequencies transmitted in theopposite direction from being lay-passed into said repeater, a onewayrepeater in said line at an intern'iediatc oint for each carrierfrequency transmitted 1n the opposite direction, a selective means forselecting the carrier frequency to be amplified thereby, and a selectivedevice on the output side of each repeater for preventing carriercurrents transmitted in said first mentioned direction from beingby-passed into said repeater.

2. In a signaling system, a transmission circuit over which a pluralityof carrier frequencies may be transmitted, means for impressing signalson each carrier frequency, a one-way amplifier corresponding to'eachcarrierfrequency associated with said transmitting circuit at anintermediate point, se lective means associated with the input side ofeach amplifier for selecting thereto the carrier frequency to beamplified, and selective means on the output side of each amplifier toprevent energy of other carrier frequencies from being by-passed intosaid repeater.

3. In a signaling system, a transmission circuit over which a pluralityof alternating carrier currents may be simultaneously transmitted inopposite directions. means for impressing signals on each carriercurrent, a one-Way amplifier for each carrier frequency transmitted,said amplifier being associated with said transmission circuit at anintermediate point, a selective circuit associated with the input sideof each amplifier for selecting thereto a single carrier frequencytransmitted in its direction of trans iss'ion, and selective devicesassociated with tie output side of each amplifier for preventingcarriercurrcnts of otherfrequencies from being by-passed into the outputof the amplifier.

4. In asignaling system. a; transmission circuit overwvl'iich aplurality of carrier frequencies may be simi'iltaneously trans emittedin the opposite direction; a group of repeaters in said circuit at anintermediate point for amplifying the carrier frequencies transmitted inone direction, a second group of repeaters for amplifying the variouscarrier frequenciestransmitted in the opposite directions. means toseparate the oppositely directed transmissions and apply them to theproper group of repeaters, and selective means to separate the variouscarrier frequencies and apply them to the proper amplifier of the group.i

t 5. In a signaling system, a pair of transmission lines over which aplurality of carrier currents may be transmitted, an intermediatestationat which said lines terminate, a plurality of channels for: superposinga'plurality of signals from said inter- Ill) mediate station upon one ofsaid lines for transmission to a distant station, a plural ity ofchannels for receiving at said intermediate station a plurality ofcarrier frequencies transmitted over the other of said ines from anotherdistant station, means associated with each of said first mentionedchannels for translating low frequency signals into carrier frequencies,and means as sociated with said first mentioned channels for.amplifying, the carrier frequencies, means associated with said secondmentioned channels for amplifying received carrier frequencies, meansassociated with said channels for translating the carrier frequenciesinto low frequency signaling currents, and means whereby the two sets ofchannels may be directly connected independently of said translatingmeans, whereby the interconnected channels constitute through amplifiersfor amplifying carrier currents transmitted from a distant stationthrough said intermediate station to another distant station.

6. In a signaling system, an intermediate station, a pair oftransmission lines extending in opposite directions to distant stations,a plurality of transmitting channels associated at said intermediatestation with one of said lines, a plurality of receiving channelsassociated at said intermediate station with the other of said lines,means associated with each transmitting channel for translating lowfrequencyssignals into carrier currents, detecting means associated witheach receiving channel, amplifying means associated with at least one ofsaid sets of channels and means for directly interconnecting thetransmitting and receiving channels independently of said translatingand detecting-means, whereby the interconnected channels with theirassociated amplifiers constitute through repeaters for carrierfrequencies transmitted from one distant station, through saidintermediate station, to another distant station.

7. In a signaling system, an intermediate station, a pair oftransmission lines extendin; in opposite directions to distant stations,a plurality of transmitting channels associated at said intermediatestation with one of said lines, a plurality of receiving channelsassociated at said intermediate station with the other of said lines,means associated with each transmitting channel for translating lowfrequency signals into carrier currents, detecting means associated witheach receiving eha nnel, amplifying means associated with at least oneof said sets of channels, and means for directly interconnecting thetransmitting and receiving channels independently of said translatingand detecting means, without disabling said detectors, whereby saidinterconnected channels with the associated amplifiers constitutethrougl'r repeaters for amplifying carrier currents transmitted from onedistant station, through said intermediate station, to another distantstation, while said detectors record the signals at the intermediatestation.

8. In a signaling system, an intermediate station, a pair oftransmission lines extending in opposite directions to distant stations,means for transmitting a plurality of alternating carrier currents oversaid lines between said distant stations, each carrier current beingtransmitted from one distant station to the other at the same frequencythroughout, means to impress signals upon each carrier current at one ofsaid distant stations for transmission to the other, and means at saidintermediatestation for impressing signals upon said carrier currents atsaid intermediate station for transmission to said distant stations.

9. In a signaling system, an intermediate station, a pair oftransmission lines extending in opposite directions to distant stations,a plurality of alternating carrier current channels for signaling oversaid lines between said distant stations, each channel employing acarrier of the same frequency throughout the entire path from onedistant station to the other, and means at said intermediate station forimpressing signals upon each of said carrier currents at saidintermediate station for transmission over said carrier channels to saiddistant stations.

10. In a signaling system, an intermediate station, a pair oftransmission lines extending in opposite directions to distant stations,a plurality of alternating carrier current channels for signaling oversaid lines between said distant stations, each, of said channelsemploying alternating carrier currents of the same frequency throughoutthe entire path from one distant station to the other, and means at saidintermediate station for impressing signals upon said carrier currentsat said intermediate station for transmission in either direction to thedistant terminal stations over each of said carrier channels.

11. In a signaling system, an intermediate station, a pair oftransmission lines extending in opposite directions to distant stations,means whereby a plurality of alternating carrier currents may betransmitted between said distant stations over said trans mission lines,each alternating carrier current being transmitted at the same frequencyfrom one distant station to the other, an amplifying repeater. for saidalternating carrier currents at said intermediate sta tion, saidrepeater amplifying each of said alternating carrier currents withoutchange in frequency, and means at said intermediate station forimpressing signals upon said carrier channels through "said repeater.

12. In a signaling system, an intermediate station, a pair oftransmission lines extending in opposite directions to distant stations,a plurality of alternating carrier current channels superposed on saidtransmission lines. for multiplex communication between said distantstations, each channel transmitting the same carrier frequencythroughout the entire path from one distant station to for impressingsignals upon said carrier channels through said repeater.

In testimony whereof, I name to this specification HERMAN A. AFFELSeptember, 1919.

have signed my 15 this 29th day of

